Remove unneeded MathObject libraries from the preloaded list

This removes the `LimitedPolynomials` and `Inequalities::common` from the list of preloaded pg libraries, since they are no longer needed (the previous commit in this branch resolves the package error issues that initiated the separation of these two macro files into separate libraries).

This pull should be accompanied by the corresponding one for the pg-dev repository that puts the `contextLimitedPolynomial.pl` and `contextInequalities.pl` files back to their original forms.

I would still recommend checking this all with `GatewayQuiz.pm`, which may need to do a freeing of MathObject libraries similar to the one I inserted in `Problem.pm`.